Amsterdam Real time was an art project that captured the invisible ‘mental map’ that every individual builds through interactions with the city. The project aimed to visualize these ‘mental maps’ through examining the mobile behaviour of the cities users. During two months, 3 October to 1 December 2002, all of Amsterdam’s residents were invited to use a tracer unit that mapped their paths. The data was visualized real-time as an animation that shows the map of Amsterdam constructing itself, not from streets or blocks of houses but from the sheer movement of its people.